Novel 1-D tube-in-tube structured NiO nanobelts were prepared by electrospinning process and subsequent onestep thermal treatment process. Nanobelt structured 1-D composite was electrospun from an aqueous solution containing poly(vinylpyrrolidone), citric acid, and dextrin which synergistically contributed to morphology control. The chemicals that optimized surface tension and viscosity of the aqueous solution enabled stable electrospinning process. Especially, dextrin played an important role in stable nanobelt formation due to its hygroscopic nature. During one-step oxidation process, the polymer composited nanobelt turned into carbonfree NiO@void@NiO tube-in-tube structured nanobelt by repeated combustion and contraction processes and Ostwald ripening mechanism. NiO tube-in-tube nanobelt prepared at 400 degrees C showed superior lithium-ion storage performances compared to those of NiO-C nanobelt and porous NiO nanobelt obtained at 300 and 500 degrees C, respectively. The discharge capacity of the tube-in-tube structured nanobelts after the 200th cycle at a current density of 1.0 A g(-1) was 992 mA h g(-1). Also, high discharge capacity of 531 mA h g(-1) at a current density of 10.0 A g(-1) proved its excellent power density. High structural stability and morphological benefits of tube-in-tube nanobelts resulted in superior lithium storage performance.